An ultrasound based method for treating objects

ABSTRACT

A method for reducing level of contaminants from an object, the method comprises introducing the object into an ultrasonic (US) bath carrying an aqueous medium that holds, suspended therein, insoluble nanoparticles and activating said bath to apply US waves onto said object while the object is at least partially submerged within said aqueous medium.

TECHNOLOGICAL FIELD

The present invention concerns the use of ultrasound techniques fortreatment of objects and in particular ultrasound based methods forremoving contaminants from various objects and products.

PRIOR ART

References considered to be relevant as background to the presentlydisclosed subject matter are listed below:

-   -   Jan C. J. Bart, Additives in Polymers: Industrial Analysis and        Applications, Wiley 2005, pg. 76    -   WO06/001293    -   US2003115794

Acknowledgement of the above references herein is not to be inferred asmeaning that these are in any way relevant to the patentability of thepresently disclosed subject matter.

BACKGROUND

Ultrasonic systems are used for various purposes. For example, Bart JanC. J. describe the utilization of ultrasonic systems for cleaningsurgical instruments, by the effect of the implosion of bubbles createdduring sonication [Jan C. J. Bart, Additives in Polymers: IndustrialAnalysis and Applications, Wiley 2005, pg. 76].

International Patent Application No. WO06/001293 describes an ultrasoniccleaning method and device for sterilizing medical appliances and forwashing hands in the purpose of disinfection in a sterilizing fluid. Theultrasonic cleaning device is structured to perform discharged ozonesterilization and silver electrolytic sterilization by silver ions onthe object to be sterilized in the sterilizing fluid.

Finally, US2003115794 describes a method for treating seeds with asolution containing at least one agent selected from the groupconsisting of a cationic surfactant, an amphoteric surfactant, abiguanide compound, an iodine compound, and an alcoholic compound, withthe aim of improving the ultrasonic cleaning effect of seeds infectedwith plant pathogens and acceleration of germination rate of the seeds.

GENERAL DESCRIPTION

The present disclosure is based on the finding that when operatingcommercially available ultrasonic baths having in the liquid mediumnano-sized particles, the cleaning effect obtained by the ultrasonic isunexpectedly better as compared to that obtained when operated withoutthe particles. This was found to be effective on various differentobjects, of various characteristics.

Thus, the present disclosure provides, in accordance with its broadestaspect, method for reducing level of contaminants from an object, themethod comprises introducing said object into an ultrasonic (US) bathcarrying an aqueous medium holding suspended therein insolublenanoparticles and activating said bath to apply US waves onto saidobject while the plant part is at least partially submerged within saidaqueous medium.

Further provided by the present disclosure is a method for reducinglevel of contaminants from a plant part, the method comprisesintroducing said plant part into an ultrasonic (US) bath carrying anaqueous medium holding suspended therein insoluble nanoparticles andactivating said bath to apply US waves onto said plant part while theplant part is at least partially submerged within said aqueous medium.

In some examples, there is also provided by the present disclosure, anobject, in particular, a plant part, comprising a maximum residue level(MRL) of less than 20% from the MRL acceptable for the harvested cropunder Regulation 396/2005, the harvested crop being obtained by themethod described above.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand the subject matter that is disclosedherein and to exemplify how it may be carried out in practice,embodiments will now be described, by way of non-limiting example only,with reference to the accompanying drawings, in which:

FIGS. 1A-1B is an image of cherry tomato samples after treatment in anultrasonic bath, with (FIG. 1A) and without (FIG. 1B) the nano-sizediamond powder present in the bath's aqueous medium, both for the sameduration of action.

FIGS. 2A-2B are images of stainless steel candle holders after treatmentin an ultrasonic bath with (FIG. 2A) and without (FIG. 2B) nano-sizealumina particles present in the bath's aqueous medium.

FIGS. 3A-3B are images of aluminum foil samples after treatment in anultrasonic bath, with (FIG. 3A) and without (FIG. 3B) nano-size diamondpowder present in the bath's aqueous medium.

FIGS. 4A-4B are images of aluminum foil samples after treatment in anultrasonic bath, without addition of nano-sized alumina particles (FIG.4A) and with (FIG. 4B) the nano-sized alumina particles.

EMBODIMENTS OF THE INVENTION

The present disclosure aims at “cleaning” objects, without causingdamage, disintegration or accelerated deterioration of the object perse, as compared the condition of the object without applying saidmethod.

In the context of the present disclosure, cleaning is to be understoodas any action of removing undesired substance from at least the surfaceof the object. The cleaning includes, without being limited thereto,disinfecting, polishing, washing off, etc. In some examples, the methoddisclosed herein can also result in an effect of reducing roughness orsmoothing at least the surface of the object being treated. Theundesired contaminants may be adhered, embedded or otherwise associatedwith the object.

The general principle of the present disclosure is the combination of USwaves with nanoparticles to achieve the “cleaning” effect.

Conventional ultrasonic baths use cavitation bubbles induced by highfrequency sound waves to activate the liquid within the bath/chamber.This cavitation activation produces high forces, by implosion viapowerful micro size liquid jets on surfaces of the treated objects, suchas metals, plastics, glass, rubber, and ceramics that result in theremoval of solid matter or contaminations adhered to the surface orwithin the object to be treated, or otherwise associated with the objectto be treated.

In some aspects, the present disclosure is based on the finding thatapplying on an object the effect of the cavitation bubbles, in thepresence of insoluble hard nanoparticles, had a better effect oncleaning the surface of the object compared to treatment of the sameobject by ultrasound alone, or by immersing the object in a disinfectingsolution. Without being bound by theory, it is believed that themicro-jets of liquid carry the nanoparticles as hard projectiles thatblast the surface with “bullets” compared to pure liquid in theultrasound cleaning without nanoparticles. This treatment of the objectis carried out by means of fluid phase nano-blasting action that removesmaterial more efficiently than pure liquid ultrasound cleaning, or byimmersing the object in a treating solution.

This improved effect was exhibited on various types of objects, withdifferent surface characteristics, from plants or plant parts such asseeds, fruits and vegetables (such as tomatoes), to metal surfaces suchas aluminum foil sheets and stainless steel candle holders.

Thus, the present disclosure provides, in its broadest aspect, a methodfor reducing level of contaminants from an object, the method comprisesintroducing said object into an ultrasonic (US) bath carrying an aqueousmedium holding suspended therein insoluble nanoparticles and activatingsaid bath to cause the formation of US waves within the bath while theobject is at least partially submerged within said aqueous medium. TheUS waves cause the movement of the nanoparticles in the bath which inturn appear to act as “scrubbers”.

In the context of the present disclosure the “object” is any solidobject that does not disintegrate in a liquid medium and/or underultrasonic vibration. The object may be of any matter.

In some other examples, the object is organic in essence. In someexamples, the organic object is a plant part.

In some examples, the “contaminant” can be any one or combination ofdirt, grease, oil, pigments, rust, algae, pathogen, fungus, bacteria,virus, lime scale, chemical compounds (e.g. biocides), flux agents,fingerprints, soot wax, mold release agents, soil, or any other matterassociated or adhered to the object and the removal of which is desired.

In some examples, the object can be defined as a solid object having aYoung modulus within a defined range. As appreciated, the young modulusdefines an object's tendency to be deformed elastically (i.e. notpermanently) when the force is applied to it. An object whose Young'smodulus is very high (e.g. above 10⁶ psi) is regarded as a rigid object,and an object whose young's modulus is low (e.g. below 10⁵ psi) isregarded as soft. Thus, in some examples, the object is inorganic inessence. In some examples, the inorganic object comprises a metal or ametal alloy. For example, metals such as gold, aluminum and silver, areknown to have a Young's modulus of 10.8×10⁶ psi, 10.0×10⁶ psi and10.5×10⁶ psi, respectively. Some metals are known to have an even higherYoung's modulus of 59.5×10⁶ psi, such as tungsten.

At times, when the object is a harvested crop, such as a fruit or avegetable, the Young's modulus is approximately similar to that ofrubber, namely, 1450 psi to 14,500 psi.

In the context of the present disclosure the term “plant part” denotesany organic plant part. The plant part may be fresh (i e immediatelyafter picking or harvesting) or preserved (i.e. some time after pickingor harvesting and being maintained under suitable storage conditions).The plant part may be a whole plant including roots, stem, leaves etc.,extracted from the soil or other medium required for its development. Insome embodiments, the plant part is a part of the plant per se.

In one example, the plant part includes at least the harvested crop,e.g. fruit, fruit body (sporocarp) or vegetable.

In one other example, the plant part includes at least the leaves.

In some other example, the plant part includes at least the seeds.

The plant may be of any kind from which a part thereof may be ofinterest, e.g. as a commercial commodity, for industry (e.g. cosmetics,pharmaceutical), for research, etc.

In some examples, the plant is any member of the group consisting ofspinach seeds, corn salad seeds, carrot, watermelon, melon, tomato,lettuce, cabbage, onion, cucumber, sweet pepper, hot pepper, squash,eggplant, pumpkin, radish, celeriac, fennel, basil, chive, coriander,dill, parsley, sugar Beet and cannabis.

In one example, the plant is spinach, and the plant part is the spinachleaves and/or spinach seeds.

In one example, the plant is corn, and the plant part is the corn seeds.

In one example, the plant is carrot, and the plant part is the carrotroot and/or carrot seeds.

In one example, the plant is watermelon, and the plant part is thewatermelon fruit and/or watermelon seeds.

In one example, the plant is melon, and the plant part is the melonfruit and/or melon seeds.

In one example, the plant is tomato, and the plant part is the tomatovegetable and/or tomato seeds.

In one example, the plant is lettuce, and the plant part is thelettuce's leaf vegetable and/or lettuce seeds.

In one example, the plant is cabbage, and the plant part is the leaffruit thereof and/or cabbage seeds.

In one example, the plant is onion, and the plant part is the onionbulb.

In one example, the plant is cucumber, and the plant part is thecucumber vegetable and/or cucumber seeds.

In one example, the plant is sweet pepper, and the plant part is thesweet pepper vegetable and/or its seeds.

In one example, the plant is hot pepper, and the plant part is the hotpepper vegetable and/or its seeds.

In one example, the plant is squash, and the plant part is the squashvegetable and/or squash seeds.

In one example, the plant is eggplant, and the plant part is theeggplant vegetable and/or eggplant seeds.

In one example, the plant is pumpkin, and the plant part is the pumpkinfruit and/or pumpkin seeds.

In one example, the plant is radish, and the plant part is the radishroot vegetable and/or radish leaves.

In one example, the plant is celeriac, and the plant part is the rootvegetable and/or celery leaves.

In one example, the plant is fennel, and the plant part is the bulband/or the leaves.

In one example, the plant is basil, and the plant part is the basilleaves and/or its seeds.

In one example, the plant is chive, and the plant part is the chiveleaves and/or its seeds.

In one example, the plant is coriander, and the plant part is thecoriander leaves and/or its seeds.

In one example, the plant is dill, and the plant part is the dill leavesand/or its seeds.

In one example, the plant is parsley, and the plant part is the parsleyleaves and/or its seeds.

In one example, the plant is sugar beet, and the plant part is the rootand/or its leaves and/or sugar beet seeds.

In one example, the plant is cannabis, and the plant part is thecannabis leaves and/or cannabis seeds.

In some examples, the plant part is the harvested crop. In this context,the harvested crop may be any part of the plant that is of commercialand/or industrial value, that is consumable by a leaving being (human aswell as animal) etc.

When the plant part comprises a fruit, the plant may be any one ofapple, banana, grape, strawberry, corn, rice, nut, pear, berry, plum,apricot, olive, cherry, peach, pineapple, kiwi, pomegranate, tomato,plum, eggplant. In some examples, the plant is selected from the Citrusfruit family, such as, without being limited thereto, lemon, lime,grapefruit, tangerine, mandarin, pomelo and orange.

When the plant part comprises a vegetable, the plant may be any one ofcucumber, squash, zucchini, herbs, rhubarb, carrot, radish, bean, pepperand pea.

In some other examples, the plant part comprises the plant's leaves.

In yet some other examples, the plant part includes the plant seeds.

In some examples, the plant part includes different parts of the plant,e.g. the bulb with the leaves attached thereto.

The object, e.g. the plant part, is introduced into the ultrasonic (US)bath for the purpose of its cleaning from contaminations. When referringto cleaning, in the context of the present invention it is to beunderstood as any level of removing contaminants from at least thesurface of the object, but not only from the surface thereof.

Depending on the object to be treated, the contaminants may vary as wellas the manner of performing the method disclosed herein. However,generally, and in accordance with its broad aspect, the method comprisesactivating the US bath for a time sufficient to reduce level ofcontaminants from the object as compared to the level thereof before theapplication of the US waves on the object. The level of contaminants maybe determined by any method known in the art and dependents on theexpected contaminant on the object to be treated, as further discussedbelow.

In some examples, the method disclosed herein permits to reduce thelevel of contaminants by at least 50% as compared to the level thereofbefore said application of the US waves. In some examples, the level ofcontaminants is reduced by at least 60%, at times, by at least 70%, oreven, at times, by at least 80%, or 90% or even 95% or 99% as comparedto the level of the same contaminant(s) before performing US bathtreatment.

In some examples, the level of contaminants is determined as compared tomaximum residual level (MRL) standards as further discussed below.

In some other examples, the level of contaminants is determined by thelevel of roughness of the object's surface (irregularities in thetexture, with the assumption that the contaminants are adhered to thesurface of the object and thus contribute to its surface roughness).Roughness or the change in roughness as a result of performing themethod disclosed herein can be determined by surface roughness average(Ra) units. Roughness is typically quantified by the vertical deviationsof a real surface from its ideal form. If these deviations are large,the surface is rough; if they are small the surface is smooth.

As noted herein, the nano-sized particles are an essential feature ofthe method disclosed herein. Without the nano-sized particles thecleaning effect of the US bath is either not apparent or is at a muchlower extent as compared to that obtained with the particles.

To the aqueous medium the water insoluble nanoparticles are added. Inthe context of the present disclosure, the water insoluble nanoparticlesare to be understood as discrete nanoscopic particles, having at leastone dimension in the nanometer scale and that they do not dissolve inwater.

In some examples, the nanoparticles are chemically inert particles. Inthe context disclosed herein it is to be understood that a “chemicallyinert” particle is one that does not react or participate in a chemicalreaction and its only function or effect is with the cleaning of theobject within the bath, i.e. the removal of the contaminants from theobject. The particles, being nano-sized, have an average diameter withinthe range of 1 nm to 1,000 nm. In some examples, the particles have anaverage diameter in the range of 2 nm to 500 nm. In some examples, theparticles have an average diameter in the range of 10 nm to 100 nm. Insome examples, the particles have an average diameter in the range of 30nm to 80 nm. In some examples, the particles have an average range of about 50 nm±10 nm.

In some examples, the water insoluble particles are of diamond powder.

In some examples, the water insoluble particles are metal oxidenanoparticles. Non-limiting examples of metal oxide nanoparticlesinclude ant member selected from the group consisting of aluminum oxidenanoparticles, zirconium oxide nanoparticles, titanium oxidenanoparticles, cerium oxide nanoparticles and mixtures thereof.

In some examples, the water insoluble particles are transition metalcarbide nanoparticles. Non-limiting examples of a transition metalcarbide is any member elected from the group consisting of siliconcarbide, titanium carbide, calcium carbide, tungsten carbide andmixtures thereof.

In some examples, the water insoluble particles are silicon oxidenanoparticles.

In some examples, the water insoluble particles are aluminum oxidenanoparticles.

In some examples, the water insoluble particles are metal nitridenanoparticles. Non-limiting examples are selected from the groupconsisting of gallium nitride, aluminum nitride, indium nitride andmixtures thereof.

In some examples, the water insoluble particles are any mixture of theabove.

In one preferred examples, the nanoparticles comprises diamond powder.

Irrespective of the matter from which they are formed, the nanoparticlescan be characterized their hardness (i.e. the property of a materialthat enables it to resist plastic deformation (usually by penetration)and/or its resistance to bending, scratching, abrasion or cutting). Insome examples, the nanoparticles are characterized by hardness in therange of 7 to 11 according to Mohs scale (typically used in mineralogy).In yet some additional or alternative examples, the particles arecharacterized by hardness in the range of 700 to 1100 according toVickers scale.

The method disclosed herein can use different amounts (concentrations)of the nanoparticles. In some examples, the nanoparticles in the US bathare at a concentration of between 0.0001% w/v to 1.0% w/v.

In some examples, the nanoparticles in the US bath are at aconcentration of between 0.0001% w/v to 0.1% w/v.

In some examples, the nanoparticles in the US bath are at aconcentration of between 0.001% w/v to 0.05% w/v.

In some examples the nanoparticles in the US bath are at a concentrationof at least 0.0001% w/v, at times, 0.001% w/v, at times, 0.005% w/v, attimes, 0.01% w/v, and further at times, 0.1% w/v.

In some examples, the nanoparticles in the US bath are at aconcentration of at most 1% w/v, at times, at most 0.5% w/v, at times,at most 0.1% w/v; at times, at most 0.05% w/v; further at times, at most0.01% w/v.

Optimization of particles density/amount may be achieved by determinedby the amount of absorption of the ultrasound by the nanoparticles.Without being bound by theory, it is assumed that high density ofnanoparticles results in less treatment (cleaning/smoothening etc)efficiency, as some of the treatment power is lost, due to absorption bythe solid nanoparticles.

When placing the object in the chamber of the cleaning bath the objectis preferably not allowed to rest on the bottom of the bath during thetreatment process, because that prevents cavitation from taking place onthe part of the object resting on the bottom of the bath (i.e. not incontact with water). Therefore, when placing the object in the cleaningchamber it is to be understood as providing contact between the aqueousmedium and the surface which needs to be treated. In some embodiments,at least 80% of the object's surface is in contact with the medium, attimes, at least 90% and further at times, about 100% coverage of thesurface with the aqueous medium, i.e. that the object is fully submergedin the medium and hanged within the chamber of the ultrasonic bath thatholds the medium.

Due to the manner of operation of the ultrasonic cleaner, uponactivation of the ultrasonic bath the nanoparticles are dispersed withinthe aqueous medium. The combined action of the cavitation bubbles andthe high energy movement of the nanoparticles within the medium (due tothe forces caused by the cavitation bubbles imploding on the surface ofthe object to be treated) lead to the “cleaning” or “smoothening” of theobject's surface.

The aqueous medium may be any medium conventionally used in ultrasoniccleaning techniques. In some embodiments, the aqueous medium is water orwater based medium. The water based medium may comprise any componentthat may assist in the cleaning action, this includes, without beinglimited thereto, detergents, wetting agents (surfactants, such aslaundry detergent) and other components, and have an influence on thecleaning process. There are various detergents and wetting agents knownto be used with ultrasonic cleaning.

The aqueous medium may, in some embodiments, comprise one or moredisinfecting agents. The disinfecting agent may be any one known in theart, such as, without being limited thereto, chloride based agents andDisodium Phosphate Anhydrous (DSP). These disinfecting agents may beused to disinfect (eradicate) any microorganism developed on the surfaceof the object.

In some embodiments, the disinfecting agent is an oxidizing agent.Oxidizing agents are known in the art and without being limited thereto,may include silver nanoparticles that release silver atoms that initiateoxidants.

The US bath is operated under conditions where the object is at leastpartially submerged in the liquid medium within the bath. In the contextdisclosed herein it is to be understood that the object does not need tobe in its entirety submerged in the liquid of the bath. In someexamples, at least the part that requires the cleaning effect issubmerged during at least part of the operation of the US waves. Thiscan be achieved by allowing the object to roll or otherwise turn overwithin the bath such that during the operation of the US bath the entiresurface of the object is exposed to the US waves and the nanoparticles.

The US bath is activated either before introducing the object into thebath or after said introducing.

In some examples, the bath is activated at a frequency range of between20 kHz to 1,500 kHz. In some examples, the activating of the ultrasonicbath is at a frequency range of between 20 kHz to 150 kHz, at times,between 40 kHz to 90 kHz.

In some examples, the bath is activated at a frequency of at least 10kHz, at times, at a frequency of at least 20 kHz, at times, of at least30 kHz, at times, of at least 40 kHz.

In some examples, the bath is activated at a frequency of at most 1,500kHz, at times, at a frequency of at most 1,000 kHz, at times, at most,900 kHz, at times, at most, 800 kHz at times, at most, 700 kHz at times,at most, 600 kHz at times, at most, 500 kHz at times, at most, 400 kHzat times, at most, 300 kHz, at times, at most, 200 kHz, at times, atmost, 150 kHz, at times, at most, 100 kHz.

In some examples, the bath is activated at an acoustic powder density inthe range of 6 W/liter to 1,500 W/liter. In some examples, the bath isactivated at an acoustic powder density in the range of 15 W/liter to150 W/liter. Yet, at times, the bath is activated at an acoustic powderdensity in the range of 4 W/liter to 65 W/liter, or at times, in therange of 10 Watt/liter to 120 Watt/liter.

The US can be operated for any length of time determined to be effectivefor removing contaminants from a particular object without causingsignificant damage to the object (i.e. damage that will cause the objectto be of no or less value). This can be determined by precedingstandardization tests for each object/contaminant or a group of objectsand/or contaminants.

In general, and in accordance with some examples, treatment inaccordance with the method disclosed herein requires operation of the USbath with the nano-sized particles for a time period from seconds to atleast 10 minutes.

In some examples, the US is activated, i.e. the US waves are applied(with the particles) onto the object for a time period of at least 10seconds, at times, 30 seconds, at times, 1 minute, at times, for atleast 5, 6, 7, 8, 9, 10, 20, 30, 40, 50 or even 60 minutes or any timeperiod in between 1 to 60 minutes.

At times, the operating time of the ultrasonic bath is between 30 sec to10 min, at times, between 20 sec to 5 min, or between 1 sec to 10 min.

In some examples, the US waves are applied for a time period of no morethan 120 minutes, at times, no more than 60 minutes, at times, no morethan 30 minutes, at times, no more than 20 minutes, at times, no morethan 10 minutes.

The temperature of the bath during its operation may vary, and willdepend inter alia on the type of the object, e.g. whether or not thetemperature may affect its quality post treatment, the type ofcontaminants, the level of contamination before treatment, the amount ofnanoparticles, the type of nanoparticles, and the operational parametersof the bath (e.g. frequency, acoustic power density etc).

In some examples, the temperature of the aqueous medium in the bath iscontrolled to be maintained to be above 1° C., at times, above 10° C.,at times, above 20° C., at times, above 30° C., and yet at times, above40° C.

In some examples, the temperature of the aqueous medium in the bath iscontrolled to be maintained below 60° C., at times, below 50° C., yet attimes, below 40° C., or even below 30° C.

In some examples, the temperature of the aqueous bath is essentiallyequal to the room temperature. This can be defined as any temperaturewithin the range of 20° C.±5° C.

In some examples, the temperature of the aqueous medium in the bath iscontrolled to be in the range of 1° C. and 60° C.

The ultrasonic bath may be of any size and shape. In some embodiments,the ultrasonic bath is selected to carry a volume of aqueous medium inthe range of 10 L to 15,000 L. As such, the method of the invention maybe suitable for both small as well as large scale treatment of objects

When the object is the plant part, the quality or performance of themethod may be determined using maximum residual level (MRL) of thecontaminants.

The effectiveness of the method disclosed herein on plant parts and inparticular crops can be defined by the maximal residual level (maximalresidue limit, MRL) of contaminants and in particular pesticides on theskin of the plant part after the treatment.

In some examples, the method provides plant part having a maximumresidue level (MRL) of contaminants of less than 30% from the MRLacceptable for said plant part under Regulation 396/2005. At times, themethod provides plant part having a maximum residue level (MRL) ofcontaminants of less than 20% from the MRL acceptable for said plantpart under Regulation 396/2005. Further, at times, the method providesplant part having a maximum residue level (MRL) of contaminants of lessthan 10% from the MRL acceptable for said plant part under Regulation396/2005.

In some examples, the contaminant is a pathogen.

The pathogen can be any agent that would cause damage to the object.

In some examples, the pathogen is or comprises fungi.

In some examples, the pathogen is or comprises a virus.

In yet some examples, the pathogen is or comprises bacteria.

When the object is a plant or plant part, the contaminant comprises atleast one plant pathogen.

In some examples, the plant part comprises seeds and the pathogen is aseed pathogen. In yet some other examples, the pathogen is oneassociated with the fruit or vegetable and/or with the leaves (herb) ofthe plant.

At times, the contaminant can comprise in addition to the pathogen perse, or alternately at least one biocide, such as those used inagriculture. The biocide can be any one or combination of insecticide,pesticides and/or nematocides.

In this connection, and in particular when treated harvested crops, itis appreciated that many agricultural crops carry on their outer skindeposited contaminants, such as biocidal (pesticidal) material, dust,dirt etc. Such contaminants are, at times, not easily removed by simplewashing with water and it is desired to provide the consumer with theharvested crop clean of such contaminants. The method disclosed hereinwas found to be efficient in removing such contaminants and smootheningthe surface of the harvested crops without damaging the outer skin ofthe crop and as such, without deteriorating the quality of the crop.

The ultrasound method disclosed herein was found effective in theremoval of contaminants that contain hazardous matter including thosecontaining Cl, F, P, S. Examples of hazardous pesticides that may beremoved by the method disclosed herein, include, without being limitedthereto, dichlorvos, diazinon, chlorpyrifos, boscalid, cyprodinil,fludioxnonil (together known as switch), methoxyfenozide, prochloraz and(sportex) lambda-cyhalothrin.

Notably, the contaminant may be at the surface of the plant part, butalso, at times, deeper in the plant part, e.g. in sub-surfaces.

Thus, in accordance with some examples, the cleaning effect of themethod disclosed herein is used to at least clean plants and plant partsfrom surface contaminants. In some embodiments, the treatment is forremoving chemical and biological residual substances, e.g. pesticidalmaterial deposited on the skin of the plant part, such as the skin of afruit or vegetable.

As noted above, the object may be other than a plant part. In someexamples, the object is an inorganic object. In some examples, theobject is composed of or at least comprises a metal or metal alloy outersurface.

In some examples, the metal is selected from the group consisting ofaluminum, gold, platinum, rhodium, silver and any combinations of same.

In some examples, the metal alloy is selected from the group consistingof stainless steel and a metal matrix composite.

In some examples, the object is composed of or comprises asemiconductor. In some examples, the semiconductor is or comprises amaterial selected from the group consisting of silicon, germanium andgallium.

At times, it is desired to merely smoothen the surfaces of inorganicobject, e.g. in accordance with the smoothening aspect. Alternatively orin addition, it is desired to remove contaminants (such as thosementioned above) from the surface of the object, such as metal and metalalloy, e.g. in accordance with the cleaning aspect.

Without being limited thereto, the metal or metal alloys may be selectedfrom the group consisting of aluminum, any type of precious metals andalloys thereof, stainless steel, cobalt-based alloys nickel-basedalloys, chromium-based alloys, molybdenum-based alloys, tantalum-basedalloys, copper-based alloys, titanium-based alloys, magnesium-basedalloys, zirconium-based alloys, tungsten-based alloys or combinationsthereof.

The precious metals may be selected from the group consisting of gold,platinum, rhodium, silver, iridium and alloys thereof.

When the object at least comprises a metal, metal alloy or semiconductorat its surface, the method is applied to at least remove solidmatter/contaminants from the surface of the object.

Performing the method disclosed herein provides a polish effect on thesurface on said object. When the object is of an inorganic material,such as a metal, metal alloy or semiconductor, the method shines orprovides a shining effect onto the surface of the object.

It was surprisingly found that operating the ultrasonic bath with thenanoparticles was effective in removing solid matter which could nothave been removed or was removed to a lower extent (less efficiently) inthe absence of the nanoparticles. In a non-limiting example describedherein, effective treatment was exhibited on the surface of stainlesssteel candle holder, which led to a polishing effect on the surface ofthe candle holder.

Further, it was surprisingly found that operating the ultrasonic bathwith the nanoparticles significantly reduced the time required in orderto remove an amount of solid matter, as compared to the time required inthe absence of the nanoparticles.

SOME NON-LIMITING EXAMPLES Example 1 Treatment of Contaminated Seedswith Ultrasound Bath Containing Nano-Sized Alumina Powder of 50 nm SizeParticles

To determine effectiveness of the method disclosed herein on the removalof contaminants from seeds, without damaging of the seeds, two sourcesof contaminated seeds were tested—spinach seeds and corn salad seeds,with the aim of preserving germination level and pathogen reductionlocated on the outer skin of the seeds.

Pathogen Reduction

Two batches of each source of the contaminated seeds were treated(namely, two batches of spinach seeds and two batches of corn saladseeds). The first batch of each seeds source was treated in fresh waterand the second batch was treated in an ultrasound water bath of 100liter, using a machine by Ultra Sonic Power Corporation of USAcontaining nano-sized alumina powder (diameter 50 nm at a concentrationof 0.01% w/v). The baths were operated at two different temperaturesaccording to Table 1 below.

After the treatment processes, the seed lots were dried to a suitablelevel required for healthy storage of the seeds.

TABLE 1 Operating parameters of the ultrasound treating bath withnanoparticles according to the method described herein and watercleaning bath Ultrasound with Parameters nanoparticles treatment Watertreatment Frequency [kHz] 40 X Acoustic power 20 X density (APD) [W/L]Temperature [° C.] 50 50 20 20 Duration [min] 30 30

Contaminated Spinach Seeds

Spinach seeds were infected with target pathogen Verticillium spp. Theinfected spinach seeds developed typical Verticillium symptoms includinga well developed mycelium web on the outer skin of the seeds.

Hot Temperature Treatment of Contaminated Spinach Seeds

A first batch of the infected seeds was placed in an ultrasound treatingbath 100 liter bath volume, made by UPC of USA comprising water andnano-sized alumina powder (diameter 50 nm at a concentration of about0.01% w/v Also, a second batch of the infected spinach seeds was soakedin a regular hot water bath (no ultrasound applied). The temperature ofboth baths was 50° C.

After 30 minutes in the baths, both the treatment of the batch of seedsin the ultrasound bath containing the nano-sized powder and thetreatment of the batch of seeds in the regular hot water bath (noultrasound applied) resulted in eradication of the Verticillium spp.

Cold Temperature (20° C.) Treatment of Contaminated Spinach Seeds

A first batch of the infected seeds was placed in a cold ultrasoundtreating bath of 100 liter bath volume, comprising water and nano-sizedalumina powder (diameter 50 nm at a concentration of about 0.01% w/v.Also, a second batch of the infected spinach seeds was soaked in aregular cold water bath (no ultrasound applied) for comparison. Thetemperature of both baths was 20° C.

After 30 minutes of treating the first batch of seeds in the coldultrasound treating bath containing nano-sized alumina powder, theVerticillium spp presence decreased from 7.5% infection presence in theas is seeds to 2% (by counting colonies forming units in a petri dish).As a result, the fungal spores eradicated and a significant part of theseed borne pathogens at the outer skin undulated seeds as well.

In comparison, after 30 minutes of soaking the second batch of seeds inthe regular cold water bath (no ultrasound applied), the Verticilliumspp presence increased from 7.5% to 21% by counting colonies formingunits in a petri dish, resulting from the spreading of the Verticilliumspp in the aqueous environment.

Contaminated Corn Salad Seeds

Corn salad seeds were infected with target pathogen Phoma fungus.Emerging seedlings show symptoms (black leaf spots, black stem and root)and finally collapse, also developing fruiting structures (pycnidiae)which are typical for Phoma can be observed on the seeds.

Germination Reduction

Samples of spinach & corn salad seeds taken from treated samples havebeen also tested for their germination capability.

Except of a slight priming effect, germination figures did notsignificantly differ after low temperature treatments compared to the asis lot. At higher temperatures and longer exposure time, germinationenergy severely decreased for the non-ultra sonic experiment.

The environment has been, according to standardized ISTA rules

Spinach germination—Pleated Papers at 15° C. (PP)

Corn Salad Germination—Top of Papers 15° C. (TP)

The sample treated with ultrasound and nano-powder at low temperaturedid not exhibit a negative side effect resulting from of the ultrasonictreatments whatsoever.

Example 2 Treatment of Contaminated Seeds with Ultrasound Bath withoutNano-Sized Alumina Powder of 50 nm Size Particles

To further determine effectiveness of the method disclosed herein on theremoval of contaminants from seeds, the contaminated seeds described inExample 1 are tested in an ultrasound treating bath with nanoparticlesaccording to the method described herein, and for comparison, in apristine ultrasound bath without addition of nanoparticles. Thegermination rate and pathogen reduction located on the outer skin of theseeds is tested after treatment of the seeds in both baths.

A first batch of the seeds source of Example 1 is treated in anultrasound water bath and a second batch is treated in an ultrasoundwater bath containing nano-sized alumina powder diameter 50 nm at aconcentration of 0.01% w/v. The baths are operated at two differenttemperatures according to Table 2 below.

After the treatment processes, the seed lots are dried to a suitablelevel required for healthy storage of the seeds.

TABLE 2 Operating parameters of the ultrasound treating bath withnanoparticles according to Example 2 and of ultrasound bath withoutnanoparticles Ultrasound with Ultrasound without Parametersnanoparticles treatment nanoparticles Frequency [kHz] 40 40 Acousticpower 20 20 density (APD) [W/L] Temperature [° C.] 50 50 20 20 Duration[min] 30 30

After treating the first batch of seeds in the ultrasound treating bathcontaining nano-sized alumina powder, the pathogen presence decreases,as a result of the eradication of the fungal spores and a significantpart of the seed borne pathogens at the outer skin of the undulatedseeds as well. However, the treating of the second bath of seeds in theaqueous ultrasound bath without the addition of nanoparticles is not aseffective for reducing the pathogen presence from the seeds and foraccelerating the germination rate.

Example 3 Treatment of Tomato with Ultrasound Bath Containing Nano-SizedDiamond Powder

To determine effectiveness of the method disclosed herein on the removalof contaminants from tomato fruits, without damaging the fruit itself,two tomatoes were coated with a yellow fluorescence material used as thecontaminating matter. The fluorescence material is made out of flakes ofabout 5 μm in size that are applied to the surface by dipping in anaqueous solution. Each tomato fruit was then placed in an ultrasoundcleaner (9 liter bath volume, MRC make Israel), the first in afresh-water bath, and the second in a water bath containing purenano-sized diamond powder (diameter 50 nm) at a concentration of about0.004% w/v.

The ultrasonic cleaners were operated using the following parameters:

-   -   Frequency of 40 kHz;    -   Acoustic power density (APD) of 20 W/L;    -   Temperature 30° C.

During operation of the ultrasonic cleaners, the tomato fruit wereobserved using a blue LED light. After the 6 minutes in the baths, thetomato in the bath containing the nano-sized diamond powder lost theyellowish fluorescent coating which means the removal of the coating.The treatment continues until the other tomato lost its yellowishfluorescent coating, after an additional 6.5 minutes, i.e. after 12.5minutes.

Images of tomatoes after ultrasound cleaning with (FIG. 1A) and without(FIG. 1B) nano-sized diamond powder. As shown (FIG. 1A), the surface ofthe nanoparticles treated tomatoes is shinier and highly reflective,indicating the removal of contaminants from the surface.

Example 4 Treatment of Stainless Steel Candle Holders with UltrasoundBath Containing Nano-Sized Alumina Powder

Two stainless steel candle holders were placed in the ultrasound cleaner(9 liter bath volume, MRC make Israel), the first in a fresh-water bath,and the second in a water bath containing nano-alumina (Al₂O₃) powder(particle size 50 nm, Sky Spring Nanomaterials, Inc.) at a concentrationof about 0.004% w/v.

The ultrasonic cleaners were operated using the following parameters:

-   -   Frequency of 40 kHz;    -   Acoustic power density (APD) of 20 W/L;    -   Temperature 30° C.

The ultrasound bath was treated for 300 minutes. An image of the twocandle holders (holder A and holder B) with and without nano-aluminapowder in the ultrasound cleaning bath is presented, respectively, inFIG. 2A (holder A) and FIG. 2B (holder B). It is noticed from this imagethat the treatment with nano-alumina powder caused a polishing effectover a larger area (FIG. 2A) compared to the non-nanoparticles treatedobject, indicative of a larger degree of removal of matter from theholder's surface that was not feasible without nanoparticles (FIG. 2B).

Example 5 Treatment of Aluminum Foil with Ultrasound Bath ContainingNano-Sized Diamond Powder

Sheets of aluminum foil were treated in ultrasonic cleaners, one withwater only and the other with nano-diamond powder (50 nm) at aconcentration of 0.004% w/v. The ultrasonic cleaners were operated asdescribed in Example 3.

The results of treatment with nanoparticles and without nanoparticlesare shown in FIG. 3, (column A and B, respectively). FIG. 3A shows thatthe treatment of the foils in the nanoparticles-treated experiment wasmore pronounced as compared to the treatment without the nanoparticlesas shown in FIG. 3B. The pieces of aluminum foil samples were etched atthe edges of the samples more prominently for the samples ofnanoparticles-treated solution.

Example 6 Treatment of Aluminum Foil with Ultrasound Bath ContainingNano-Sized Particles Powder

Two sheets of aluminum foil were treated in ultrasonic cleaners, onewith water only and the other with nano-alumina powder (50 nm at aconcentration of 0.01% w/v). The ultrasonic cleaners were operated asdescribed in Table 3.

TABLE 3 Operating parameters of the ultrasound cleaning bath withnanoparticles according to Example 6 and of ultrasound bath withoutnanoparticles Ultrasound with Ultrasound without Parametersnanoparticles cleaning nanoparticles Frequency [kHz] 40 40 Acousticpower 20 20 density (APD) [W/L] Temperature [° C.] 12 12 Duration [sec]20 20

The results of treatment without (FIG. 4A) and with (FIG. 4B)nanoparticles. FIG. 4B shows that the amount of perforations of thealuminum foil treated in the nanoparticles experiment is greater ascompared to the treatment without the nanoparticles (FIG. 4A), while thesize of the perforations exhibited in FIG. 4B is much smaller than theperforations exhibited in FIG. 4A.

1. A method for reducing level of contaminants from an object, themethod comprises introducing said object into an ultrasonic (US) bathcarrying an aqueous medium holding suspended therein insolublenanoparticles and activating said bath to cause US waves in the mediumwhile the object is at least partially submerged within said aqueousmedium; wherein said bath is activated at a frequency of at most 150kHz; wherein said nanoparticles are at a determined density; and whereinsaid nanoparticles are chemically inert.
 2. The method of claim 1,wherein said object is a plant part. 3-5. (canceled)
 6. The method ofclaim 1, comprising activating the ultrasonic bath for a time sufficientto reduce level of contaminants from the object as compared to the levelthereof before said application of the US waves.
 7. The method of claim6, wherein said level of contaminants is reduced by at least 50% ascompared to the level thereof before said application of the US waves.8-9. (canceled)
 10. The method of claim 1, wherein the nanoparticleshave an average diameter in the range of 1 nm to 1,000 nm. 11.(canceled)
 12. The method of claim 1, wherein the water insolublenanoparticles are selected from the group consisting of diamond powder,metal oxide nanoparticles, silicon oxide nanoparticles, transition metalcarbide nanoparticles, metal nitride and mixtures thereof.
 13. Themethod of claim 12, wherein the water insoluble nanoparticles arediamond powder.
 14. The method of claim 12, wherein the water insolublenanoparticles are metal oxide nanoparticles selected from the groupconsisting of aluminum oxide nanoparticles, zirconium oxidenanoparticles, titanium oxide nanoparticles, cerium oxide nanoparticlesand mixtures thereof.
 15. The method of claim 12, wherein the waterinsoluble nanoparticles are transition metal carbide selected from thegroup consisting of silicon carbide, titanium carbide, calcium carbide,tungsten carbide and mixtures thereof.
 16. The method of claim 12,wherein the water insoluble nanoparticles are metal nitride selectedfrom the group consisting of gallium nitride, aluminum nitride, indiumnitride and mixtures thereof.
 17. The method of claim 1, wherein thenanoparticles are characterized by a hardness in the range of 7 to 11according to Mohs scale or by a hardness in the range of 700 to 1100according to Vickers scale.
 18. (canceled)
 19. The method of claim 1,wherein the nanoparticles in the US bath are at a concentration ofbetween 0.0001% w/v to 0.1% w/v.
 20. The method of claim 1, comprisingactivating the US bath at a frequency range of between 20 kHz to 150kHz.
 21. The method of claim 20, comprising activating the ultrasonicbath at a frequency range of between 10 kHz to 90 kHz.
 22. The method ofclaim 1, comprising activating the US bath at an acoustic power densityin the range of 6 W/liter to 1,500 W/liter.
 23. The method of claim 22,wherein said acoustic power density is in the range of 10 Watt/liter to120 Watt/liter.
 24. The method of claim 1, wherein said activating ofthe US bath is for a time period of from 1 min to 60 25-28. (canceled)29. The method of claim 1, wherein said object is a plant part, and saidmethod provides a plant part having a maximum residue level (MRL) ofcontaminants of less than 20% from the MRL acceptable for said plantpart under Regulation 396/2005.
 30. The method of claim 1, wherein saidobject is a plant part and said contaminant comprises at least onepathogen. 31-33. (canceled)
 34. The method of claim 1, wherein saidobject comprises a semiconductor, metal or metal alloy surface. 35-37.(canceled)